Automatic telephone system



E JAUCH AUTOMATIC TELEPHONE SYSTEM Filed Nov. 15, 1938 VNSR Jan. 14, 1941.

INVENTOR: EUGEN JAUCH Z ATTORNEY.

Patented Jan. 14, 1941 UNITED STATES PATENT GFF'ICE AUTOMATIC TELEPHONE SYSTEM Application November 15, 1938, Serial No. 240,572 In Germany November 1, 1937 Claims.

The invention relates to a circuit arrangement for automatic telephone systems in which connections of different value can be set up, e. g., local and trunk connections. v y The invention concerns the control of the extension of calling current to the calling set according to the value of the incoming connection; and this is done by associating switching means with the calling line, which are influenced over the selector which Ais seized, according to the value of the incoming connection and determine which kind of calling current is to be extended to the desired subscribers set.

'I'he arrangement is such that the switching means, when they come into effect, inter-change the conductors of the junction lines of the calling subscribers. Preferably the switching means is iniiuenced over the test lead of the final selector Which is seized, to which earth potential is connected over the test relay of the selector when a low valued connection is concerned, while with a high valued connection earth potential is connected directly. The characterizingof the value of the connection .also depends on whether the low resistance winding of the test relay in the test conductor is connected to the iinal selector or not. Since it is diicult to control the switch means in series with the test conductor directly in dependence on whether the test relay is connected or not as in the two cases the current ratios are only slightly diierent, the system is arranged so that' switching means in the form of a switching relay first comes into ef fect with each type of incoming connection but then, however, in connections of one kind, e.v g.,

high valued connections, is immediately disconnected.r In order to carry out these switching operations, according to the invention the switching relay has an associated auxiliary relay which, 40 in the case of one particular connection, makes the switching relay ineffective by short circuiting the energizing winding of this relay and connecting the holding winding of the switching relay parallel to theswitch means in the test conductor ofthe seized final selector. Since in the case of high valued connections these lead directly to earth potential, the holding winding of the switching relay is short-circuited in such cases so that the switching relay is released. 'I'he arrangement according to the invention can be used with advantage particularly in sys-- tems in which the call current is connectedto one conductor of the junction line on a high valued connection and to the other conductor on a low valued connection. In such systems there exists the special difculty of using two junctions b-y which the subscriber is calledover one conductor and earth. In order to insure the calling of the desired subscriber of a two-junction arrangement, in such cases, according to the v invention, calling current is connected to the selector in a different manner for different Valued connections and is disconnected by changing over the leads of the common junction line leading to both subscribers in common in dependence on the value of the incoming connection.

The invention can also be used with advantage in systems in which the calling current is connected in the same way to the junction lines on both high and low valued connections. In this Acase a differentiation in the characterizing of the incoming connections of different value is made possible by connecting differentl calling members, characterizing the type of incoming connection, in dependence on the extension of the calling current to the calling subscriber by means of the switching relay according to the value of the incoming connection.

The combination local and trunk nal selectors OFLWI of Fig. 1 and OFLW2 of Fig. 2 may be of the well known Strowger type final selector such as is disclosed in the Taylor Patent 2,113,119, issued April 5, 1938, modied slightly to meet the requirements of this invention. Referring to Figs. 1 and 2 of the Taylor patent, it is to be noted that the iinal selector may be seized over two paths', one including the negative l, positive l, and PI conductors and the other path including the negative 2, positive 2, and P2 conductors. In accordance with the present invention, it will be assumed that when local or low valued connections are extended to the final selector they willalways seize the final selector over conductors positive I, negative I, and Pl and when trunk or high Valued connections are extended' they will always seize the final selector over conductors positive 2, negative 2 and P2.

The relay WS of the Taylor patent is provided in series with the positive 2 conductor and is energized whenever the switch is seized over the path including this conductor to determine the wiper set to be used in extending the connection to the desired subscriber. In the present invention, however, the relay WS may be utilizedto discriminate between low and high valuedconnections instead of the wiper set to be used.

When'used in the final selector OFLWI of Fig. 1, the relay WS may be modified to include contacts In, 2n and 311. which would be normally closed and contacts 14h, liih and |672 which would be normally open contacts. Therefore, when a local or low valued connection is extended to the final selector OFLWI, the contacts In, 211 and 311 would be closed and when a trunk or high valued connection is extended to the final selector, relay WS would energize to disconnect contacts |11, 2n and 311 and to connect contacts Mh, |h and lih for the purpose to be described hereinafter.

When used in the final selector OFLW2 of Fig. 2 the relay WS may be modiedto include contacts |811, n, and 2in which would be normally closed and contacts I'lh, h and 25h which would be normally open contacts. When a low valued connection is extended to the final selector OFLWZ, the contacts |8n, 1t, and 2|1z would be closed and when a trunk or high valued connection is extended to the final selector relay WS would energize to disconnect contacts |811, 1t, and 2|1z. and to connect contacts l'lh, h, and 25h for the purpose to be described hereinafter.

It should be understood that the above method of discrimination is only one of a number of arrangements well known in the art for performing a specific controlling function in a selector, which is determined over one of a plurality of paths over which the selector may be seized.

Embodiments of the invention are shown in the accompanying drawing. In the drawing all details not necessary for the understanding of the invention are not shown.

In Fig. l an arrangement for two dierent kinds of junctions is shown, which are connected to a combination local and trunk final selector (OFLW) in which the calling current is connected to the b-conductor for high valued connections and to the a-conductor for low valued connections.

Fig. 2 shows an arrangement for an individual subscribers connection in which several calling members are provided which are connected according to the value of the incoming connection.

The method of working of the arrangements shown in the embodiments is as follows:

In Fig. l after the setting of the final selector (OF'LW) by an incoming low valued connection and after testing to see whether the line is free in dependence on the control switch of this selector the contacts In, 211. and 311. are closed to send out calling current. If, for example, the sublscriber 'Inl is called the following circuit is made: earth, battery, relay Tl of the preselector, c-conductor, relay Fl (winding I), contacts dgl, 5f|, c-arm of the line selector on contact contact 311., relay PI, earth. In this circuit the switching relay FI operates and opens its contact 5fl. In this way the relay Gl is energized in series with relay FI by way of its winding I and by closing its contact 69|, short-circuits the winding I of the relay FI. The relay GI further closes the contact 'lgl and thus connects its winding II and also the winding II of the switching relay FI; these two windings which are connected with one another in series are now in parallel to the switching devices arranged in the test circuit in the final selector.

Since in the above case a low valued connection is concerned the relay Pl is connected in the test path of the final selector over the contact 3h. Parallel to this relay, relay FI is maintained energized over its winding II so that contacts 8f| and Sfl shifted to their operated positions, remain in these positions and switch through the lines to the desired subscribers junction. The alternating calling current now connected from the final selector over the contact |1t to the alead extends therefore from the calling current source over: contact |11, a-arm of the nal selector to contact l, Contact MI, a-lead of the junction line, contact |Elu2, relay Ul, subscriber Thi over the condenser Kl, in parallel to the balancing coil Dfrl, contact Hui to earth. The subscriber Tn! is therefore called. Vhen he replies, relay UI is operated and over the Contact llul in its operated position connects the subscriber T1t| to the junction line, while by opening the contact |2u| disconnects the second subscriber from the common junction line.

When the connection is terminated the winding I of the relay Gl is still connected in series with this winding II and the winding II of the relay Fl after the release of the final selector. Since the relay Gl is a differential relay the two windings are in opposition so that the relay Gl restores. Thus the contact lg! is also opened and the holding circuit for the relays Fl and Gi is interrupted. The switching device is therefore in itsl normal position.

If the subscriber Th2 is called for a low valued connection corresponding switching operations are performed which are differentiated from the operations described for subscriber Tnl in so far as the final selector is not set on contact but on contact 2. The calling current to the subscriber Th2 then extends from the calling current source over: contact |11, a-arrn of the final selector to contact 2, contact 9f| in itsI operated position, b-conductor of the junction line, contact iui, relay U2, subscribers set T112, condenser KZ, contact |3u2 to earth. When the calling subscriber lifts up his receiver relay U2 energizes and connects the subscriber to the common junction line over contact |3u2 and over contact ||lu2 disconnects the second subscriber T1L|.

In the case of an incoming high valued connection (trunk connection) to the subscriber Tnl, the final selector is again set on the Contact After the testing to `see whether this is free the contacts lfih, |5h and lh are closed, by the control switch of the final selector. Thus over the c-conductor a circuit isI first made for the relay Fi which in this case extends from earth, battery, relay Tl in the preselector, relay FI (winding I) contacts fiel, Efl, c-arm of the inal selector on contact contact ISh directly to earth. Relay FI, therefore, operates again and, in the manner already described, by opening the contact 5f| connects the winding II of the relay Gl, which now over the contact ligl, shortcircuits the winding I of the relay Fi while at the same time, over the contact '|g|, windings II of the relays F and G are connected. These two windings are now in parallel to the the contact lh in the c-conductor of the final selector seized, which extends directly to earth potential. The two windings are therefore short-circuited so that the relay FI whose winding is already shortcircuited over the contact gl, restores and remains disconnected for the duration of the connection; the relay GI remains energized in the test conductor, however. The contacts afl and afl are restored to normal so that the calling current sent out from the final selector extends over the following path: source contact lh, b-arm of the line selector to contact contact Sfl, a-conductor of the junction line, contact lout, relay UI, subscribers set Tnl, condenser Kl, contact ||u|, earth. Therefore, in spite of the connection of calling current alternating current F to the other lead the calling subscriber 'Inl is reached over the a-conductor. When he replies there follows the .connection to the common line in the manner already described. On the release of the connection after the release of the final selector, the winding II of the relay GI, which has been short-circuited over contact Hh in the nal selector, energizes and effects the release of this relay as it works in opposition to winding I.

In the case of an incoming high valued connection to the subscriber T'n2, corresponding switching operations take place which are only differentiated in that the iinal selector is set on the contact 2 so that the alternating calling current connected over the contact i571. extendsover the b-arm of the nal selector to contact 2, contact 8fl in the normal position, b-lead of the junction line, contact l2al, relay U2, subscribers set T712,

condenser K2, contact |3112 to earth.

The arrangements for making outgoing connections are not described in detail since they are not of interest in connection with the present invention.

Fig. 2 relates to a system in which the calling current is connected at the iinal selector (OFLWZ) in the same way (over the control switch contacts Hh or I8 1L) to the a-conductor of the nal selector for incoming high and low valued connections. Since, however, a differentiation between incoming high and low valued connections lis undertaken by the control switch of the iinal selector it is possible by using the switching device already described in Fig. 1 to characterize the incoming local and trunk connections at the connected subscribers set.

In the case of incoming low valued connections, after the setting of the nal selector on the contact of the calling Set the following circuit is closed: earth, battery, relay T2 in the preselector, c-conductor, relay F2 (winding I), contact |9g2, 2012, c-arm of the line selector on contact 3, control switch contact 2| n, relay P2, earth. The switching relay F2 operates and in the manner already described with reference to Fig. 1, operates the auxiliary relay G2 which connects its winding II and thus, also the winding II of relay F2. Since the low valued connection is concerned, the relay F2 remains energized with its winding II parallel to the relay P2 in the nal selector and operates its contacts 22f2 and 2312.

, The calling current of the nal selector therefore extends over the contact |811, a-arm of the final selector, contact 3, contact 22f2, a-conductor of the junctio-n line, switchhock Mhu, bell Wn, earth. The bell for low valued connections sounds and gives the calling subscriber an indication of the kind of incoming connection. When the calling subscriber replies, the bell as disconnected together with the bell for high valued connections connected over the b-conductor.

In the case of incoming high valued connections, the energizing of relay F2 takes place due to the earth potential connected directly over the control switch contact h. in the final selector. In this way, after the operation of relay G2 in the manner already described, the winding II of the relay F2 is short-circuited also in the manner described so that the relay F2 immediately restores and the contacts 22f2 and 2312, respectively remain in their rest position for the duration of the connection. The calling current sent out from the final selector therefore extends from the calling current source over: contact l'lh, a-arm of the iinal selector on contact 3, contact 22f2, b-conductor of the junction line, switch hook contact 26h12, bell Wh to earth. The alarm bell Wh, for high valued connections sounds and does this in a different tone to the sound produced for low valued connections. When the subscriber lifts his receiver the calling circuit is interrupted and the conversation can be proceeded with.

The release of the switching over device takes place in the manner described in connection with Fig. 1. f

What'is claimed is: n

1. In an automatic telephone system arranged for local and toll calls, a line, switching means individual to said lines, a connector switch operated to connect with said line when either a local or a toll call is extended thereto, and a source of signalling current in said switch, said switching means controlled according to the value of the connection extended to said line to determine the conductor of the line over which said signalling current shall'be transmitted.

2. In a system as claimed in claim 1 in which the switchingv means reverses the conductors of said line upon operation.

3. In an automatic telephone system arranged for local and toll calls, a line, a connector switch operated to connect with said line when either a local or a toll call is extended thereto, a test circuit for said switch, switching means individual to said line controlled over said test circuit to determine the conductor of the line over which signalling current is to be transmitted, means effective when a local call is extended to said line for connecting ground to said test circuit through a test relay of said connector to thereby control said switching means, and means effective when a toll call is extended to said line for connecting direct ground to said test circuit to thereby control said switching means.

4. In a system as claimed in claim 3, wherein said switching means is operated over said test circuit when either a local or a toll call is extended, and means controlled responsive to the extension of a toll call for immediately restoring said switching means to normal.

5. In a system as claimed in claim 3, wherein said switching means comprises a two winding relay, the rst of said windings connected in series with said test circuit and the second of said windings connected in parallel with the test relay in the test circuit of said connector and functions as a holding winding.

6. In a system as claimed in claim 1, an auxiliary relay associated with said switching means operated responsive to the extension of a toll call to said line to thereby render said switching means ineffective.

7. In an automatic telephone system arranged for local and toll calls, a line, switching means individual to said line, a connector switch operable to connect with said line responsive either to a local or toll call, a source of signalling current, means responsive to the operation of said switch to connect with said line for connecting said signalling current thereto, a switching means controlled according to the value of the connection for determining over which conductor of the line the ringing current is to be transmitted, an auxiliary differential wound relay associated with said switching means operated over a circuit including one of its windings responsive to the extension of a toll call to render said switching means ineiective, and

means eiective upon the release of an established connection for completing an energizing circuit for both windings of said relay to restore the same to normal.

8. In a telephone system, a line, a connector switch for extending local or toll calls to said line. a test circuit for said switch, a source of ringing current in said switch, switching means individual to said line and included in said test circuit for determining the conductor of the line over which the ringing current is to be transmitted when a connection is extended thereto, and means in said connector for connecting ground through a resistance to said test circuit when a local call is extended and for connecting direct ground to. said test circuit when `a toll call is extended and thereby control the operation of said switching means.

9. In a telephone system, a line, a station on said line, a pair of signalling devices for said station, an exchange switch, said switch adapted to be operated for the extension of either a toll or local connection to said line, a source of signalling current in said switch, and means for connecting said signalling current to said line, said signalling current connected to one conductor of said line to actuate one of said signals when local calls are extended and connected to the other conductor of said line to actuate the other of said signals when toll calls are extended.

10. In a telephone system, a line, a station on said line, two separate signals at said station, a circuit for each signal, a switch adapted to be directively operated to extend either a local or a toll call to said station, a source of signalling current in said switch, means responsive to the extension of a local call to said station for connecting said signalling current to said line over one circuit to actuate only one of said signals, and means responsive to the extension of a toll call to said station for connecting said signalling current over the other circuit to isaid line to actuate only the other of said signals.

EUGEN JAUCH. 

